Protective layer for mitigating protruding defects in magnetic tape recording media

ABSTRACT

A magnetic recording medium according to one embodiment includes an underlayer and a magnetic layer above the underlayer. The magnetic layer includes a first magnetic material and particulates. A solid protective layer is positioned above the magnetic layer, the protective layer including a second material. At least some of the particulates of the magnetic layer protrude completely through the protective layer. A method for forming a magnetic recording medium according to one embodiment includes forming a magnetic layer above a substrate, the magnetic layer including a first magnetic material and particulates, and forming a solid protective layer above the magnetic layer to a thickness whereby some of the particulates protrude through the protective layer and are exposed along an upper surface of the protective layer.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to magnetic tape recording mediahaving reduced occurrence of protruding defects.

In magnetic storage systems, magnetic transducers read data from andwrite data onto magnetic recording media. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

In a tape drive system, the drive moves the magnetic tape over thesurface of the tape head at high speed. Usually the tape head isdesigned to minimize the spacing between the head and the tape. Thespacing between the magnetic head and the magnetic tape is crucial andso goals in these systems are to have the recording gaps of thetransducers, which are the source of the magnetic recording flux in nearcontact with the tape to effect writing sharp transitions, and to havethe read elements in near contact with the tape to provide effectivecoupling of the magnetic field from the tape to the read elements.

SUMMARY

A magnetic recording medium according to one embodiment includes anunderlayer and a magnetic layer above the underlayer. The magnetic layerincludes a first magnetic material and particulates. A solid protectivelayer is positioned above the magnetic layer, the protective layerincluding a second material. At least some of the particulates of themagnetic layer protrude completely through the protective layer.

A method for forming a magnetic recording medium according to oneembodiment includes forming a magnetic layer above a substrate, themagnetic layer including a first magnetic material and particulates, andforming a solid protective layer above the magnetic layer to a thicknesswhereby some of the particulates protrude through the protective layerand are exposed along an upper surface of the protective layer.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a tape drive system, which may include a magnetic head, adrive mechanism for passing a magnetic medium (e.g., recording tape)over the magnetic head, and a controller electrically coupled to themagnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 1B is a schematic diagram of a tape cartridge according to oneembodiment.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one embodiment.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A.

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one embodiment where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIG. 8A is a magnetic recording medium with a protective layer,according to one embodiment.

FIG. 8B is a magnetic recording medium with a protective layer,according to one embodiment.

FIG. 9 is a magnetic recording medium with a protective layer, accordingto one embodiment.

FIG. 10 is a magnetic recording medium with two protective layers,according to one embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofmagnetic storage media.

In one general embodiment, a magnetic recording medium includes anunderlayer and a magnetic layer above the underlayer. The magnetic layerincludes a first magnetic material and particulates. A protective layeris positioned above the magnetic layer, the protective layer including asecond material.

In another general embodiment, a magnetic recording medium includes abase film and a first nonmagnetic layer above the base film. The firstnonmagnetic layer has first nonmagnetic particles. A second nonmagneticlayer is positioned above the first nonmagnetic layer, the secondnonmagnetic layer having second nonmagnetic particles. A magnetic layeris positioned above the second nonmagnetic layer, the magnetic layerincluding a magnetic material.

In yet another general embodiment, a method for forming a magneticrecording medium includes forming a magnetic layer above a substrate,the magnetic layer including a first magnetic material and particulates,and forming a protective layer above the magnetic layer, the protectivelayer including a second material.

FIG. 1A illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128, may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc. The controller 128 may include at least oneservo channel and at least one data channel, each of which include dataflow processing logic configured to process and/or store information tobe written to and/or read from the tape 122. The controller 128 mayoperate under logic known in the art, as well as any logic disclosedherein, and thus may be considered as a processor for any of thedescriptions of tape drives included herein, in various embodiments. Thecontroller 128 may be coupled to a memory 136 of any known type, whichmay store instructions executable by the controller 128. Moreover, thecontroller 128 may be configured and/or programmable to perform orcontrol some or all of the methodology presented herein. Thus, thecontroller 128 may be considered to be configured to perform variousoperations by way of logic programmed into one or more chips, modules,and/or blocks; software, firmware, and/or other instructions beingavailable to one or more processors; etc., and combinations thereof.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (internal or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneembodiment. Such tape cartridge 150 may be used with a system such asthat shown in FIG. 1A. As shown, the tape cartridge 150 includes ahousing 152, a tape 122 in the housing 152, and a nonvolatile memory 156coupled to the housing 152. In some approaches, the nonvolatile memory156 may be embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred embodiment, the nonvolatile memory 156 may be aFlash memory device, ROM device, etc., embedded into or coupled to theinside or outside of the tape cartridge 150. The nonvolatile memory isaccessible by the tape drive and the tape operating software (the driversoftware), and/or other device.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 3 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B may be made of the sameor similar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 32 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

FIG. 2B depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2B of FIG. 2A. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative embodiments include 8, 16, 32, 40, and 64 activereaders and/or writers 206 per array, and alternatively interleaveddesigns having odd numbers of reader or writers such as 17, 25, 33, etc.An illustrative embodiment includes 32 readers per array and/or 32writers per array, where the actual number of transducer elements couldbe greater, e.g., 33, 34, etc. This allows the tape to travel moreslowly, thereby reducing speed-induced tracking and mechanicaldifficulties and/or execute fewer “wraps” to fill or read the tape.While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2B, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complementarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write transducer 214 and the readers, exemplified by the readtransducer 216, are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R/W pair, exemplified by the R/Wpair 222. Note that the intended direction of tape travel is sometimesreferred to herein as the direction of tape travel, and such terms maybe used interchangeably. Such direction of tape travel may be inferredfrom the design of the system, e.g., by examining the guides; observingthe actual direction of tape travel relative to the reference point;etc. Moreover, in a system operable for bi-direction reading and/orwriting, the direction of tape travel in both directions is typicallyparallel and thus both directions may be considered equivalent to eachother.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (−),cobalt zirconium tantalum (CZT) or Al—Fe—Si (Sendust), a sensor 234 forsensing a data track on a magnetic medium, a second shield 238 typicallyof a nickel-iron alloy (e.g., ˜80/20 at % NiFe, also known aspermalloy), first and second writer pole tips 228, 230, and a coil (notshown). The sensor may be of any known type, including those based onMR, GMR, AMR, tunneling magnetoresistance (TMR), etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one embodimentincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyembodiments of the present invention. One skilled in the art apprisedwith the teachings herein will appreciate how permutations of thepresent invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one embodiment ofthe present invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one embodiment, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These embodiments are particularly adaptedfor write-read-write applications.

A benefit of this and other embodiments described herein is that,because the outer modules 302, 306 are fixed at a determined offset fromthe second module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.3° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller α₃tends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one embodiment, the second module 304 includes aplurality of data and optional servo readers 331 and no writers. Thefirst and third modules 302, 306 include a plurality of writers 322 andno data readers, with the exception that the outer modules 302, 306 mayinclude optional servo readers. The servo readers may be used toposition the head during reading and/or writing operations. The servoreader(s) on each module are typically located towards the end of thearray of readers or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is20-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some embodiments, the second module 304 has a closure, while thefirst and third modules 302, 306 do not have a closure. Where there isno closure, preferably a hard coating is added to the module. Onepreferred coating is diamond-like carbon (DLC).

In the embodiment shown in FIG. 5, the first, second, and third modules302, 304, 306 each have a closure 332, 334, 336, which extends the tapebearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan commonly-used LTO tape head spacing. The open space between themodules 302, 304, 306 can still be set to approximately 0.5 to 0.6 mm,which in some embodiments is ideal for stabilizing tape motion over thesecond module 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an embodimentwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this embodiment, thereby reducing wear on the elements in thetrailing module 306. These embodiments are particularly useful forwrite-read-write applications. Additional aspects of these embodimentsare similar to those given above.

Typically, the tape wrap angles may be set about midway between theembodiments shown in FIGS. 5 and 6.

FIG. 7 illustrates an embodiment where the modules 302, 304, 306 are inan overwrap configuration. Particularly, the tape bearing surfaces 308,312 of the outer modules 302, 306 are angled slightly more than the tape315 when set at the desired wrap angle α₂ relative to the second module304. In this embodiment, the tape does not pop off of the trailingmodule, allowing it to be used for writing or reading. Accordingly, theleading and middle modules can both perform reading and/or writingfunctions while the trailing module can read any just-written data.Thus, these embodiments are preferred for write-read-write,read-write-read, and write-write-read applications. In the latterembodiments, closures should be wider than the tape canopies forensuring read capability. The wider closures may require a widergap-to-gap separation. Therefore a preferred embodiment has awrite-read-write configuration, which may use shortened closures thatthus allow closer gap-to-gap separation.

Additional aspects of the embodiments shown in FIGS. 6 and 7 are similarto those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. oralternatively by outriggers, which are integral to the head. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the embodiments described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads. Moreover, unless otherwisespecified, processes and materials of types known in the art may beadapted for use in various embodiments in conformance with the teachingsherein, as would become apparent to one skilled in the art upon readingthe present disclosure.

Servo pattern and data read sensors may experience shorting failuresduring normal data writing and/or reading operations. Particularly, suchshorting may be caused by defects (herein “defects”) that protrude fromthe magnetic tape recording media (also generically referred to as“tape”), such as agglomerations of for example abrasive nonmagneticparticulates and/or binder materials; or other defects, e.g., hardparticulates, that protrude from the tape surface. For example, as iswell known for tape media in particular, larger foreign particles, e.g.,remnants of alpha-hematite production, may be present in a layer orlayers of the media. Such defects may be in the form of a particle(solid or agglomeration) that has a dimension, e.g., diameter or lengthalong most distant points thereof, that is at least twice as great as anaverage diameter of the particles in the layer having similar materials,e.g., smaller particles similar to those that have agglomerated to formthe defect. In some cases, the defect may have a dimension that isgreater than a thickness of the layer and so is the source of thedefect.

Whatever the source or composition, such defects, when protruding fromthe upper surface of the medium, may smear and/or plow conductivematerial from the thin films of the reader across the sensor, therebycreating an electrical short.

While this issue is relevant to both current-in-plane and moreparticularly to current-perpendicular-to-plane (CPP) readers in general,this problem is particularly problematic with CPP TMR sensors. Becausethe deposition thickness of the tunnel barrier the TMR sensor is verythin, e.g., less than about 10 angstroms in some approaches, smearing ofconductive material thereacross is a pervasive problem. Accordingly, TMRsensors may be particularly susceptible to such shorting due to the thinsensor barrier.

Interactions between tape media surface defects and a sensor surface mayalso lead to friction-related functionality issues. For example, when asurface defect passes over a sensor, friction may lead to plasticdeformation of one or more delicate thin films of the sensor. Plasticdeformation of the delicate thin films may alter the stress distributioninside the sensor, and this may be presented as noise due to magneticinstability, e.g., switching magnetic domains.

Narrower write heads may also be subject to degradation via spacing lossresulting from gouges caused by tape surface defects.

Such surface defects may result from, e.g., the milling of particlesused in the manufacturing process of the tape, e.g., where a largeparticle becomes captured in a coating of the tape media duringmanufacture; a manufacturing defect during any known manufacturingprocess, such as creation of an agglomerate of particulates or binderthat protrudes from the media; etc.

Embodiments described herein include implementing a thin protectiveovercoat on a layer of the tape media, to help mitigate tape mediadefect abrasivity.

FIGS. 8A and 8B depicts sections of a magnetic recording medium 800 inwhich tape media surface defects are minimized, in accordance with oneembodiment. As an option, the present magnetic recording medium 800 maybe implemented in conjunction with features from any other embodimentlisted herein, such as those described with reference to the other FIGS.Of course, however, such magnetic recording medium 800 and otherspresented herein may be used in various applications and/or inpermutations which may or may not be specifically described in theillustrative embodiments listed herein. Further, the magnetic recordingmedium 800 presented herein may be used in any desired environment.Moreover, except where specifically specified, various components may beof conventional construction.

The magnetic recording medium 800 may be any type of magnetic recordingmedium that includes protruding defects 802. For example, the magneticrecording medium may be a magnetic tape.

The magnetic recording medium 800 may include a conventional underlayer808. The underlayer 808 may be added as a smoothing layer over the basefilm 810. The underlayer 808 may be positioned above a conventional basefilm 810 and back coat 812 of the magnetic recording medium 800. Forexample, the base film 810 may include a known aramid, polyethylenenaphthalate, polyethylene terephthalate, etc. The magnetic recordingmedium 800 may include a magnetic layer 806 above the underlayer 808.Other and/or alternative conventional layers may be present in this andother embodiments described herein. Illustrative thicknesses for thevarious layers include a base film thickness of about 2000 to about 6000nanometers, an underlayer thickness of about 800 to about 2000nanometers, and a total thickness of all magnetic layers of about 50 toabout 100 nanometers. Of course these thicknesses are exemplary only,and various embodiments may have layers of greater or lesser thicknessthan the illustrative ranges presented herein.

The magnetic layer 806 may include a first magnetic material andnonmagnetic particulates 801 which are different than the magneticmaterial.

The nonmagnetic particulates 801 of the magnetic layer 806 may be anytype of conventional nonmagnetic particulates, e.g., added for thepurpose of cleaning the magnetic head. For example, according to oneapproach, the particulates may include aluminum oxide, chromium oxide,silicon carbide, etc.

The magnetic material in the magnetic layer 806 may include one or moreknown magnetic materials, including those conventionally used formagnetic tape media. According to one approach, the magnetic material inthe magnetic layer 806 may include barium ferrite.

For purposes of an example, the magnetic recording medium 800 is shownto include a defect 802. The defect 802 shown in FIG. 8A is one or moreagglomerations of particulates 801, e.g., where the agglomeration isformed during extrusion of the magnetic layer 806. Such agglomerationmay be a cluster of nonmagnetic particulates 801, a cluster of magneticparticulates, or a cluster of magnetic and nonmagnetic particulates, anyof which may also include binder.

The defect 802 may also and/or alternatively include a denseagglomeration of materials, e.g., an agglomeration of α-hematite, or aforeign particulate in the nonmagnetic underlayer 808. See FIG. 8B,showing a larger defect 802.

In either case, the defect 802 may protrude from the magnetic layer 806,e.g., in the direction D. As noted above, such protruding defect, if notmitigated, could cause smearing of conductive material across a TMRsensor as it passes across a magnetic head.

In one approach, the defect 802 may be described as an “iceberg” profiledefect. An iceberg profile defect may extend through one or more otherlayers of the magnetic recording medium and protrude out of a layer of amagnetic recording medium.

For example, the defect 802 shown on the left hand side of FIG. 8B maybe described as having an iceberg profile, because the larger portion ofit extends through the magnetic layer 806 and a “tip” protrudes abovethe magnetic layer 806 in direction D which is perpendicular to theplane of deposition P of the various layers.

The protruding portion of the iceberg profile defect 802 may measureabout 5-70 nm, e.g., in direction D, while, the underlying portion,e.g., the non-protruding portion may extend 750-1500 nm into the tape inthe thickness direction.

With continued reference to FIG. 8B, in some cases, the magnetic layer806 and/or protective layer 804 may also protrude in the vicinity of thedefect 802, e.g., as shown at the defect 802 on the right hand side ofthe Figure.

Such defects 802 have been described elsewhere above to be “surfacedefects”, where “surface” may denote that such defects would otherwisebe protruding from an uppermost layer in conventional magnetic recordingmedium, such as a magnetic tape. In sharp contrast however, defects,e.g., defect 802, of the magnetic recording medium 800 and/or one ormore other embodiments described herein may be described without the“surface” pre-text, as such defects, e.g., defect 802, preferably do notprotrude from the surface of the magnetic recording medium 800 when themagnetic recording medium includes a protective layer 804, as will nowbe described below.

The magnetic recording medium 800 may include a protective layer 804above the magnetic layer 806. The protective layer 804 may include asecond material. The second material is nonmagnetic in some approaches.In other approaches, the second material is magnetic, and may be thesame or different than the first magnetic material of the magnetic layer806. In some embodiments, the protective layer 804 is non-magnetic orweakly magnetic.

The second magnetic material of the protective layer 804 may include anyknown magnetic material. According to one approach, the magneticmaterial in the protective layer 804 may include barium ferrite.

The protective layer 804 may be viscous when formed to promote theprotective layer 804 to settle around any defects that may protrudethrough the protective layer 804, enveloping such defects or at leastreducing their effective extent of protrusion.

As shown in FIGS. 8A and 8B, the protective layer 804 may physicallyenvelop the entire protruding portion of some of the defects 802 thatprotrudes outward from/above the magnetic layer 806.

The protective layer 804 may also and/or alternatively physicallyenvelop a substantial portion, e.g., at least 85% of the protrudingsurface area, of the defect 802 that protrudes outward from/above themagnetic layer 806. Physically enveloping all or a substantial portionof the protruding portion of the defect 802 may prevent the defect 802from causing a sensor shorting event and/or damaging the thin films of areader.

To prevent formation of agglomerations in the protective layer 804, theprotective layer 804 may be constructed of a material that does notcontain nonmagnetic particulates therein when formed. However, otherembodiments may include a protective layer 804 with particulatestherein.

It should be noted that some of the particulates of the magnetic layer806 may protrude through the protective layer 804. Any particulates ofthe magnetic layer 806 that protrude through the protective layer 804may be considered to be part of the magnetic layer 806 and not amaterial of the protective layer 804.

A thickness T₁ of the protective layer 804 may preferably not be athickness that would completely cover/physically envelope all of theparticulates of the magnetic layer 806 that may protrude through theprotective layer 804. Having a thickness T₁ of the protective layer 804that does not completely cover or physically envelope all of theparticulates of the magnetic layer 806 may desirably promote cleaning ofthe head, e.g., see head 126 of FIG. 1A, and/or prevent stiction of themagnetic recording medium to the head. For example, suppose the worstcase protrusion would be about 55 nm above the surface of the tapewithout the protective layer 804. For some heads, this may be enough tocause shorting. In this case, a 15 nm protective layer may be sufficientto effectively reduce the protrusion to 40 nm, which may be sufficientto mitigate shorting. In this case it may be preferable to slightlyincrease the density or median protrusion of the particulates in themagnetic layer.

The thickness T₁ of the protective layer 804 is preferably not so thinas to leave a portion of the defect 802 protruding above the protectivelayer 804, e.g., in a direction D.

According to one approach, the thickness T₁ of the protective layer 804may be at least 10% of the total thickness T₂ of the magnetic recordingmedium 800 in direction D, which is perpendicular to a plane ofdeposition P of the protective layer 804.

In a preferred approach, the total thickness T₃ of the magnetic andprotective layers is a design magnetic thickness of the magneticrecording medium.

The protective layer 804 may be an outermost layer of the magneticrecording medium 800. Accordingly, a lubricant on the outer surface ofthe medium should not be considered an outer layer in some embodiments.

The protective layer 804 of the magnetic recording medium 800 mayhowever according to some embodiments include a lubricating material.For example, a lubricating material may be embedded in the protectivelayer 804. In such an approach, any embedded lubricating material thatmay migrate through the protective layer 804, e.g., in a direction D, toany area above the protective layer 804, again may or may not beconsidered an outer layer of the protective layer 804 and/or anoutermost layer of the magnetic recording medium 800.

FIG. 9 depicts a magnetic recording medium 900 in accordance withanother embodiment. As an option, the present magnetic recording medium900 may be implemented in conjunction with features from any otherembodiment listed herein, such as those described with reference to theother FIGS. Of course, however, such magnetic recording medium 900 andothers presented herein may be used in various applications and/or inpermutations which may or may not be specifically described in theillustrative embodiments listed herein. Further, the magnetic recordingmedium 900 presented herein may be used in any desired environment.

Components of the magnetic recording medium 900 may be similar to thoseof magnetic recording medium 800 of FIG. 8A. For example, the magneticrecording medium 900 may include a conventional base film 910 above aback coat 912.

The magnetic recording medium 900 may include a nonmagnetic underlayer902 above the base film 910. The nonmagnetic underlayer 902 may havefirst nonmagnetic particles and, in some embodiments, conventionalparticulates that are of a different material than the first nonmagneticparticles, and are also preferably weakly magnetic or nonmagnetic.

The first nonmagnetic particles may include any suitable nonmagneticmaterial. According to one approach, the first nonmagnetic particles mayinclude α-hematite.

The magnetic recording medium 900 may include a second nonmagnetic layer904 above the underlayer 902. The second nonmagnetic layer 904 may havesecond nonmagnetic particles which may be the same as or different thanthe first nonmagnetic particles. Nonmagnetic particulates may or may notbe present in the second nonmagnetic layer.

Similar to the first nonmagnetic particles, the second nonmagneticparticles may include any suitable nonmagnetic material. According toone approach, the second nonmagnetic particles may include α-hematite.

It should be noted that the first nonmagnetic particles of theunderlayer 902, and the second nonmagnetic particles of the secondnonmagnetic layer 904 may include nonmagnetic materials of the sameand/or different type, depending on the embodiment.

For purposes of an example, the underlayer 902 is shown to include adefect 802. The defect 802 may include dense agglomerations of materialcreated during formation of the underlayer 902. The defect 802 may be inthe form of a particle (solid or agglomeration) that has a dimension,e.g., diameter or length along most distant points thereof, that is atleast 50% larger than an average diameter of the particles in theunderlayer. In some cases, the defect 802 may have a dimension that isgreater than a thickness of the underlayer 902.

The magnetic layer 906 may include a magnetic material, e.g., any knownmagnetic material, preferably in a binder. According to one approach,the magnetic material in the magnetic layer 906 may include bariumferrite.

Similar to the protective layer 804 of the magnetic recording medium800, the magnetic layer 906 of the magnetic recording medium 900 mayphysically envelop a portion of the defect 802 that protrudes outwardfrom/above the underlayer 902, e.g., to prevent the defect 802 fromcausing a sensor shorting event.

A thickness T₅ of the second nonmagnetic layer 904 may preferably be athickness that would at least partially cover and/or physically envelopesuch defects 802 of the underlayer 902 that would otherwise protrudeinto and/or through the magnetic layer 906.

The relative thickness of the magnetic layer 906 compared to a thicknessT₄ of the magnetic recording medium 900 may vary depending on theforming thicknesses of one or more of the layers of the magneticrecording medium 900.

FIG. 10 depicts a magnetic recording medium 1000 in accordance withanother embodiment. As an option, the present magnetic recording medium1000 may be implemented in conjunction with features from any otherembodiment listed herein, such as those described with reference to theother FIGS. Of course, however, such magnetic recording medium 1000 andothers presented herein may be used in various applications and/or inpermutations which may or may not be specifically described in theillustrative embodiments listed herein. Further, the magnetic recordingmedium 1000 presented herein may be used in any desired environment.

The magnetic recording medium 1000 in the embodiment shown combinesfeatures of the mediums 800, 900 of FIGS. 8 and 9. Particularly, themagnetic recording medium 1000 includes the same lower layers as themedium 900 of FIG. 9, but with the first and second magnetic layers 806,804 as in FIG. 8A replacing the magnetic layer 906 of FIG. 9. Theelements of FIG. 10 therefore have common numbering with the associatedlayers of FIGS. 8 and 9.

One or more layers of the magnetic recording mediums described hereinmay be formed using a known process. Such known processes may be adaptedto create a medium having the desired features described herein.

According to one approach, processes for forming the magnetic recordingmedium may include depositing materials of the layers using otherwiseconventional forming techniques, e.g., lamination, extrusion,co-extrusion, etc.

The forming thicknesses of one or more of the layers of the one or moremagnetic recording mediums described herein may vary, e.g., depending onthe dimensions of defects expected to be included in the magneticrecording medium, depending on spatial constraints of the media drive inwhich the magnetic recording medium will be used, depending on theconstraints that would be easily identified by one skilled in the artupon reading the present description, etc.

According to the same and/or a different approach, formation of themagnetic recording medium may include forming at least the secondnonmagnetic layer above the underlayer using extrusion, e.g. with ablade.

According to one approach, one or more extrusion heads may be used toform one or more of the layers of the magnetic recording media. Thelayer materials may be formed to the same and/or varying thicknesses.

According to preferred embodiments, various layers of the magneticrecording medium may be extruded sequentially or co-extruded, andthereby cure together.

According to yet other approaches, one or more of the layers may beapplied via spraying or the like. This may provide a more conformalcoating.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

The inventive concepts disclosed herein have been presented by way ofexample to illustrate the myriad features thereof in a plurality ofillustrative scenarios, embodiments, and/or implementations. It shouldbe appreciated that the concepts generally disclosed are to beconsidered as modular, and may be implemented in any combination,permutation, or synthesis thereof. In addition, any modification,alteration, or equivalent of the presently disclosed features,functions, and concepts that would be appreciated by a person havingordinary skill in the art upon reading the instant descriptions shouldalso be considered within the scope of this disclosure.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A magnetic recording medium, comprising: an underlayer; a magnetic layer above the underlayer, the magnetic layer including a first magnetic material and particulates; and a solid protective layer above the magnetic layer, the protective layer including a second material, wherein at least some of the particulates of the magnetic layer protrude completely through the protective layer.
 2. The magnetic recording medium as recited in claim 1, wherein the second material is magnetic, wherein a composition of the protective layer is different than a composition of the magnetic layer.
 3. The magnetic recording medium as recited in claim 2, wherein a total thickness of the magnetic and protective layers is a design magnetic thickness of the magnetic recording medium.
 4. The magnetic recording medium as recited in claim 1, wherein the second material is nonmagnetic.
 5. The magnetic recording medium as recited in claim 1, wherein the protective layer is constructed of a material that does not contain the particulates.
 6. The magnetic recording medium as recited in claim 1, wherein the protective layer is an outermost layer of the magnetic recording medium.
 7. The magnetic recording medium as recited in claim 1, wherein a thickness of the protective layer is at least 10% of a total thickness of the magnetic recording medium.
 8. The magnetic recording medium as recited in claim 1, wherein the first magnetic material in the magnetic layer includes barium ferrite.
 9. The magnetic recording medium as recited in claim 1, wherein the second material in the protective layer includes barium ferrite.
 10. The magnetic recording medium as recited in claim 1, wherein the particulates include aluminum oxide.
 11. The magnetic recording medium as recited in claim 1, wherein some of the particulates protrude beyond and are thereby exposed along an upper surface of the protective layer.
 12. The magnetic recording medium as recited in claim 1, comprising a lubricating material embedded in the protective layer.
 13. The magnetic recording medium as recited in claim 12, wherein the lubricating material is configured to migrate through the protective layer.
 14. The magnetic recording medium as recited in claim 1, comprising a lubricant on an outer surface of the protective layer, the lubricant having a different composition than the protective layer.
 15. A method for forming a magnetic recording medium, the method comprising: forming a magnetic layer above a substrate, the magnetic layer including a first magnetic material and particulates; and forming a solid protective layer above the magnetic layer to a thickness whereby some of the particulates protrude through the protective layer and are exposed along an upper surface of the protective layer.
 16. The method as recited in claim 15, comprising adding a lubricant on an outer surface of the protective layer.
 17. The method as recited in claim 15, wherein the protective layer is viscous when formed.
 18. The method as recited in claim 15, wherein a composition of the protective layer is different than a composition of the magnetic layer.
 19. The method as recited in claim 15, wherein at least one of the layers of the magnetic recording medium is formed using extrusion.
 20. The method as recited in claim 15, wherein at least two layers of the magnetic recording medium are co-extruded, and are cured together. 